Thermostat



April 16, 1940.

H. A. MULVANY 'I'HERMOSTAT Filed June 6, 1938 IIll'fl'llliillllllllllllllllll l Illlmmmmli Ill mmmmnnlllllllllllllllllllllllilllllm' TJ III/II, l

IIIIIIIIIII INVENTOR. W a.

A TTORNEY.

Patented Apr. 16, 1940 UNITED STATES PATENT OFFICE 'rnmmos'rar HarryAlfred Mul'vany, Berkeley, Calif. Application June 6, 1938, Serial No.211,974

This invention relates to thermostats, and especially to thermostats ofthe bl-metallic type.

In the operation of refrigerator cars, particularly during the wintermonths, heaters have been installed to prevent the temperature fromdropping below the freezing point or some other predetermineddestructive temperature. In conjunction with such heaters, thermostatshave been used to turn the heaters automatically off and on, as thetemperature increases or decreases within the refrigerator car, butalthough a number of thermostats have been employed, they have not beenaltogether satisfactory, as they are not suiliciently rugged towithstand the vibration, jars and shocks to which the cars are subjectedduring transit, and in addition thereto, they have usually been toocomplicated for the average trainman to adjust and take care of themproperly.

The object of the present invention is generally to improve and simplifythe construction and operation of thermostats; to provide a thermostatwhich consists of few parts and which is rugged in construction; toprovide a thermostatv which may be readily applied or attached toheaters of varying types; to-provide a thermostat in which an actuatinglever is the only movable part and a single screw the only adjustablepart; to provide a thermostat which is composed of a single expandiblemember, to

- which 11: secured a pair of substantially nonexpanding members, saidmembers being flexible and bowed in opposition to each other to permitdoubling or compounding of the movement of the expanding member; toprovide means whereby the compounding movement of the substantiallynon-expanding, but flexible, members is transmitted to operate anactuating lever; and further, to provide an adjustment whereby theactuating lever becomes operative only at predetermined temperatures.

The thermostat is shown by way of illustration in the accompanyingdrawing, in which:

Fig. 1 isa side elevation of the same, said figure also showing themanner in which the base member are pairs of pads 2-2 and 3-4, 7

and extended lengthwise of the base and secured to the respective pairsof pads are strips 4 and 5 constructed of a material which issubstantially non-expansible; a suitable material, and that which isactually employed, is a metal known to 6 the trade as Invar. TheInvarstrips are flexible, and they are bowed in opposition to each other, asclearly shown inFig. 1, and as the base or expandible member lengthensor short ens due to temperature changes, the bow in the 10 respectivestrips changes. This change in the bowing of the strips is transmittedto operate a pivotally mounted actuating lever, and this is accomplishedas follows.

Secured or formed on the strip 4 is a pair of 15 spaced lugs 6, andpivoted at one end between said lugs is an actuating lever I. Secured tothe strip 5 is a nut I, and extending and engaging thelever I is anadjusting screw 9. By this arrangement movement is transmitted to swingthe lever about the pivot 8, and at the same time it is possible tocompound or double the movement of the base or expandible member and totransmit the compounding movement to the lever I. For instance, if thetemperature is 55 cooling or dropping, the base A will contract and thebow in the strip 4 will consequently increase, thereby causing thepivotal point 6 to movein the direction of arrow a. The bow in the strip5 willsimilarly increase, and the ad- 30 lusting screw will accordinglymove in the opposite direction, or that indicated by the arrow 2:. Theadjusting screw will in that instance function as a fulcrum point forthe lever i, and

as the pivotal point 6 and the fulcrum point 8 move inopposite'directions, pr towards each other, the contracting movement ofthe expandible member is compounded, with the result that considerablemovement is imparted to the actuating lever even though the temperaturechange is comparatively slight.

The thermostat is here shown as connected 1 with a needle valve l5 whichcontrols the flow of fuel to a burner, and if the burner is em- 45ployed in conjunction with a heater in a refrigerator car, thethermostat will automatically open the valve and increase the flow offuel as the temperature drops below a predetermined point. Thispredetermined point is regulated by 50 the adjusting screw 9, and forthis reason the screw is provided with an enlarged head 9a, whichcarries a temperature-indicating scale II. Also, the peripheral edge ofthe head is knurled or roughened, and itis engaged by aspring arm 5pointer H (see Fig. 2), so as to normally secure the head and screwagainst rotation.

Thus, if it is desired to turn on the heater when the temperature in arefrigerator car drops to 34 F., the head So is rotated until 34 on thetemperature scale registers with the pointer H, and when thistemperature is reached, the valve begins to open and the heater willgradually give off more' heat and prevent a further temperature drop.Conversely, if the temperature rises, the valve will close, and auniform predetermined temperature is thus automatically maintr ned.

The thermostat is exceedingly simple and rugged in construction, theonly moving part employed being the actuating lever l, and the onlyadjustable part being the screw 9, and as this is normally held againstrotation by the spring arm or pointer H, vibrations, shocks and the likeimparted to the thermostat during transit of the car will in no waychange the temperature adjustment. The trainman has only one thing todo, and that is to rotate the head So of the adjusting screw to set thethermostat for any temperature required, and that certainly does notrequire any skill. Other care or attention on the part of the trainmenis entirely unnecessary, as the chances of breakage or of parts gettingout of adjustment is just about nil.

In fact, the thermostat as a whole is so simple in construction that themechanism is usually covered. For this reason sides I4 and ends 15 areformed on the base plate A, enclosing the strips 4 and 5 and theactuating lever. A cover plate indicated by dotted lines at l6 may thusbe applied, and the thermostat is substantially tamper-proof. The onlyparts projecting from the thermostat are the end of the control lever 'land the adjusting screw 9 and its head So.

While the actuating lever l is here shown as connected to actuate aneedle valve, such as shown at 55, it is obvious that it may be employedfor many different purposes, and may be connected in different ways. Forinstance, lever i might be connected to actuate the contacts of anelectric switch, relay, or similar mechanism. Sufiice it to say that theactuating lever projects from one end of the base member, and as suchmay be readily connected in difi'erent ways with a mechanism to beactuated, and thus it is a simple matter to attach the thermostat tomechanisms of different types and character.

While certain features of my invention have been more or lessspecifically described and illustrated, I nevertheless wish itunderstood that changes may be resorted to within the scope of theappended claims, and that the specific materials and finish of the partsemployed may be such as the maker desires or various uses dictate.-

Having thus described and illustrated my invention, what I claim anddesire to secure by Letters Patent is:

1. A thermostat comprising an elongated holder formed of a thermallyexpansible material, a pair of non-expanding fiexible members normallybowed in opposition to one another lengthwise of the holder and anchoredat their opposite ends thereto, a lever extending in the direction ofits length between said members and projecting at its outer end beyondthe holder, and connections between said members and the opposite endportion of said lever at spaced points in the length of the latter, oneof said connections including a pivot support anchored intermediate theends of its respective flexible member, in which the extreme inner endof the lever is pivoted, and the other of said connections including anadjusting screw, the inner vend of which bears against the lever at apoint spaced from its pivot and is otherwise free thereof, and

a tubular nut anchored in connection with the other flexible member andthrough which said adjusting screw works to a point beyond one side ofthe holder.

2. A thermostat comprising an elongated boxlike holder formed of athermally expansible material and having openings at one end and intermediate one side thereof, a pair of non-expanding members bowed inopposition to one another and disposed lengthwise within the holder andanchored at their ends thereto, a lever extending between said membersand projecting at its outer end exteriorly oi the holder through saidend opening, and connections between said members and the inner portionof said lever at spaced points in the length of the latter, one of saidconnections including a pivotal support for the inner end of the lever,and the other connection including an adjustable screw bearing at itsinner end against the lever and otherwise free thereof, and a tubularnut secured to the corresponding. bowed member and through which saidadjusting screw works to the exterior of the holder through the saidside opening thereof.

HARRY ALFRED MULVAN

